?Thanks to Daniel for suggesting I try burning my ISO image with brasero in response to my problems burning images using nautilus. Unfortunately brasero won't offer me a burn ISO option 497226: brasero: Burn button disabled. No indication of why.. I just tried wodim directly and ended up with the same (wrong) sum for the burnt disc as with nautilus cd burner (not suprising really).

I wondered if I was being bitten by 386640: wodim doesn't fixate DVD+R with premastered ISO, but trying to fix the disc did not update the sum.

Taking an image of the burnt disc, I notice that the burnt image is longer size-wise than the input ISO by 10240 bytes. This turns out to be 10240 of zeroes appended to the image.